Unearthing Aftershocks: Physical Simulations, Statistical Models, and New Observations

地震不是单独发生的孤立事件，而是成群发生的事件。在地震之后，会发生许多较小的余震，称为余震，其频率随着地震发生后的时间而降低。偶尔，其中一次余震甚至比引发它的主震还要大。了解这些余震很重要，因为它们不仅能让我们了解地震过程，而且对社会来说也是一种切实可行的措施，因为了解它们有助于更好地准备和从大地震的后果中恢复过来。这项工作的目的之一是发展科学知识，有助于开发地震业务预报能力的新努力，这将为应急管理人员提供自动化工具，利用余震集群特性接收实时更新的预报，以便更好地量化灾害，用于响应、恢复和规划，以及与更广泛的公众进行外联和沟通。该项目的研究人员是开发该系统的团队的一部分。地震余震是一种特别有趣的现象，因为它们已被证明具有各种各样的统计规律，但从本质上讲，仍未被理解，因为尚未开发出能够再现所有统计规律的物理模型。在没有物理模型的情况下，已经建立了一些统计模型，以发展综合目录和预测方法，以及其他用途。但究竟要包括哪些统计成分仍不确定。本建议旨在通过各种方法对余震有更好的物理认识，并以一些有用的方式应用这种认识。提出了三个具体要素。一种是新的物理模型，该模型将断层视为多链粗糙表面集，能够再现断层的时空特征和生产力统计。二是一种新型的统计测量方法，利用靠近破裂区的余震丰度，更好地解决了余震与主震之间的空间关系。第三是建立一套新的统计模型，与时间相关的风险模型相结合，使推广能够纳入观测结果所表明的新的不可分离的震级-空间核。在这些要素中的任何一个方面取得成功，都可以进一步帮助量化地震危害，通过改进对基于经验的地面运动关系成分的物理理解，用于估计和设计工程需求，以及在操作地震预测中的缩放和聚类行为，这是一种在大地震后的响应和规划中具有重要社会用途的工具。该项目将有助于培训和指导一位早期职业科学家。该项目还将支持PI参与开发业务地震预报能力的组织WGCEP（加利福尼亚地震概率工作组）及其应用NEPEC（国家地震预测评估委员会）。

Earthquakes occur not as single isolated events, but as clusters of events. In the aftermath of an earthquake, many smaller ones happen, called aftershocks, at a rate which decreases with the time following an event. Occasionally one of the aftershocks is even larger than the mainshock that triggered it. These aftershocks are important to understand, both for the insights they give us into earthquake processes, but also as a practical measure for society, as understanding them better aids in preparing for and recovery from the aftermath of a large earthquake. One aim of this work is to develop scientific knowledge which can contribute to a new effort to develop Operational Earthquake Forecast capabilities, which will provide automated tools for emergency managers to receive real-time updated forecasts using aftershock clustering properties to better quantify hazards, for use in response and recovery and planning, as well as outreach and communication to the broader public. The investigators on this project are part of a team working to develop that system.Aftershocks of earthquakes are particularly interesting phenomena in that they have been shown to have a wide variety of statistical regularities, and yet remain, at the core, not understood, in the sense that a physical model has yet to be developed which can reproduce all the statistical regularities. In the absence of a physical model, a number of statistical models have been built to develop synthetic catalogs and forecasting methods, among other uses. But what statistical ingredients to include remain uncertain. This proposal seeks to develop a better physical understanding of aftershocks from a variety of approaches, and apply this understanding in a number of useful ways. Three specific elements are proposed. One is a new physical model, which treats a fault as a multi-stranded rough set of surfaces, and is capable of reproducing the spatio-temporal features and productivity statistics. The second one is a new type of statistical measurement, which uses the abundance of aftershocks close to the rupture area to better resolve the spatial relationships among aftershocks and the mainshock. The third one is a new set of statistical models to integrate with time dependent hazard models, enabling generalizations to incorporate the new non-separable magnitude-spatial kernels indicated by the observations. Success in any of these elements could further help in quantifying earthquake hazards, through improved physical understandings of ingredients in empirically based ground motion relations used to estimate and design for engineering demands, and scaling and clustering behavior in operational earthquake forecasting, a tool of significant societal use in response and planning in the aftermath of a large earthquake. The project would aid in the training and mentoring of an early career scientist. The project would also support the participation of the PI in organizations developing operational earthquake forecasting capability, WGCEP (Working Group on California Earthquake Probabilities), and their application, NEPEC (National Earthquake Prediction Evaluation Council).